1. Field of the Invention
The present invention relates to an Electron Emission Device (EED) that controls background-brightness by adjusting a voltage of scanning signals, and more particularly, to an EED that reduces a voltage difference between a scanning signal voltage and a data electrode line voltage in proportion to a discharge current to reduce background-brightness due to collisions between a few electrons and an anode when data is not being supplied to an electron emission display panel.
2. Description of the Related A
An EED includes an electron emission display panel and a driving device for driving the electron emission display panel. When a positive voltage is supplied to a gate electrode and a negative voltage is supplied to a cathode while a driving device supplies a relatively positive voltage to an anode of the electron emission display panel, electrons are emitted from the cathode and accelerated toward the anode by the potential difference between the gate electrode and the cathode, and then, light is generated by the electrons colliding with the fluorescent cells of the anode.
The gate electrode and the cathode of the electron emission display panel are respectively electrically connected to one of a data electrode line and a scan electrode line. In the course of sequentially supplying scanning signals to the scan electrode line, if a pulse width or a pulse size having a voltage proportional to the brightness is supplied to the data electrode line, electrons are emitted from the cathode by the potential difference between an electrode (the gate electrode or the cathode) connected to the scan electrode line and an electrode (the cathode or the gate electrode) connected to the data electrode line and the electrons are accelerated toward the anode.
The data electrode line and the scan electrode line are disposed on a rear panel (a lower plate) of the electron emission display panel, and the high voltage anode and the fluorescent cells are disposed on a front panel (an upper plate) of the electron emission display panel. Manufacturing a thinner electron emission display panels have been studied to meet market requirements.
However, since the anode of the electron emission display panel is operated at a high voltage of 1-4 KV, a tendency to emit electrons from the cathode, even if the voltage difference between the gate electrode and the cathode does not exceed the discharge firing voltage Vth, occurs as the electron emission display panel becomes thinner. Even if no data signals are supplied to the electron emission display panel, that is, when at least one frame or more than 60 frames are not supplied (that is, “0” data is supplied), electrons are emitted from the cathode and collide with the fluorescent cells of the anode. Therefore, An electron emission display panel looks grey to the viewers. Hereinafter, the brightness of the panel when data is not supplied will be referred to as “background-brightness.”
Accordingly, contrast decreases as the background-brightness increases when no data is supplied, thereby requiring a method of reducing the background-brightness.